OpenCL SDK for Quartus Prime 15.1

You can choose the software version in the download page where it says "Select release". here (http://dl.altera.com/15.1/?edition=standard&platform=linux&download_manager=direct) is a direct link to the page for Quartus Prime Standard 15.1. You can find a link to the OpenCL SDK-only installer from the "Additional Software"tab. If you need Quartus Prime Pro (Arria 10 only), change "standard" to "pro" in the link.